Light-weight metal squeeze casting of golf clubs

ABSTRACT

An improved method and process of golf club manufacture is presented where some or all the components of the clubs are squeeze-cast or metal injection molded from light-weight metals. Components can be made of different metal alloys and then separately heat treated and then finally assembled by mechanical means.

BACKGROUND OF THE INVENTION

This invention relates to the technology of metal casting and particularto the technology of casting golf club heads, components, and clubs.

BRIEF SUMMARY OF THE INVENTION

This present invention is a method and means of casting state-of-the-artgolf club parts out of magnesium and other light-weight metals byapplying existing squeeze-casting or metal injection molding (MIM)technology to the unique problems of golf club manufacture. Metals thathave been used to cast golf club components can also be squeeze cast ormade by MIM. Such metals include aluminum, titanium, and magnesium.

Squeeze casting of aluminum golf club parts has already beenaccomplished. The present invention applies squeeze casting and MIMtechnology to light weight metals such as magnesium and titanium. Thesqueeze-cast golf club parts, primarily heads, can then be machined andassembled together.

The weight of golf club heads can be significantly reduced by usingsqueeze cast or MIM casting for head components. The weight savings canprovide room for specialized weighting of the golf club head toaccomplish various design and performance goals.

OBJECTS AND SUMMARY OF THE INVENTION

Squeeze casting, or semi-solid casting, is a process of melting thesubject metal alloy, pouring it into a half-open vertical mold/die,allowing it to become semi-solid, and then applying the top half of thedie with pressure during the solidification process. The cast is madewith less pressure than required for ordinary forging and produces aproduct that is less porous and mechanically stronger.

Parts possessing greater detail and incapable of being forged can becast by these methods, reducing machining and improving strength of thedetail sections. Automobile parts requiring high-quality metalconstruction, particularly safety features such as brakes and steeringcomponents, are now made by squeeze casting.

Squeeze-cast parts are more easily heat-treated and can be more readilywelded, due to their low porosity. This means that unique golf club headproperties such as strong bodies and hard face plates and sole platescan be accomplished by squeeze-casting or MIM casting. MIM parts can beproduced from ferrous and non-ferrous metals and alloys.

The method proposed is that components be squeeze cast or MIM cast outof separate magnesium or other metal alloys and treated separately, suchas heat-treating face and sole plates to heat them for hardness. Thecast parts need less machining because of the qualities of the castmetal, reducing unique golf club production costs. Finally, componentscan be welded, screwed or glued together more successfully due to thehigher-quality, low porosity cast metal parts.

As a separate goal, this invention uses squeeze casting to producehollow golf club heads with minimal weight combined with maximumstrength, so that custom weighting of the head can be performed. All ofthe light weight metal golf club head components can be squeeze cast,including titanium sole plates and face plates.

As an additional goal, this invention allows the manufacturer to controlthe thickness of the metal in the walls of the club head and therebycontrol the weight.

DETAILED SPECIFICATION

Pursuant to this invention, precision castings of golf club components,such as putter heads and driver heads, sole, and face plates, can beachieved. Cast metal golf club parts that have complex inner geometriesor require high-quality finishes can be produced without expensivemachining. Light-weight metals such as aluminum, titanium, and magnesiumalloys can be successfully cast in this manner, as well as various steelalloys.

The steps involved in applying squeeze casting to golf club manufactureinvolve 1) designing a mold or molds for the golf club parts, takingadvantage of the unique properties of squeeze-casting to producehigh-quality, light-weight metal parts, 2) selecting the appropriatealloy to be cast, based on intended strength, weight, and hardness ofthe part, 3) pre-heating the mold to receive the metal to be cast, 4)pouring a semi-solid mass of the alloy selected in 2) into the mold, 5)using the ram of the squeeze-casting machine to push the semi-solidmetal into the mold with a pressure determined by the selection of metaland the tensile qualities desired in the part, 6) removing the finishedpart from the mold and performing subsequent trimming and finishingwork.

The MIM process begins with the atomization of molten metal to formmetal powders. Then, the metal powder is sieved followed by gasclassification to alter the particle size distribution. The metal powderis mixed with thermoplastic binders to produce a homogeneous feedstock;with approximately 60 volume % metal powder and 40 volume % binders.Then, the feedstock is placed into an injection molder and molded toform a net shape green part.

Injection molding occurs at relatively low temperatures and pressures inconventional plastic injection molding machines. The molds are similarto those used for plastic injection molding including slides andmulti-cavity configurations. After injection molding, two thermalprocesses occur. First, the binder is removed from the green part via anevaporative process called “debinding.” Second, after debinding the partis sintered to form a high-density metal part. Sintering occurs at hightemperatures, up to 2300° F. (1260° C.), near the melting point of themetal; under a dry H₂ atmosphere or inert gas atmosphere.

During sintering, the part will shrink isotropically to form a denseshape. Since, the complex shape of the molded part is retained throughthe process, close tolerances in the as-sintered part can be achieved.Scrap is eliminated or significantly reduced since machining of the partafter sintering is usually not necessary.

As a continuation of the described process of this invention, magnesiumand titanium face and sole plates cast with the above squeeze-castingprocess can be further heat treated to harden them and prepare them tobe attached to the club head. This hardening can be carried out withoutaffecting the tensile strength of the club head bodies cast by thismethod, which are cast from different alloys and not heat treated.

This invention uses the above process, including several steps standardin squeeze--casting and MIM-casting, and applies it to aluminum,titanium and magnesium parts for golf clubs and for other purposes. Thepreferred embodiment is applying this process to golf club head partscomprised of magnesium or titanium alloys. Other applications of thisinvention can be made to other metal alloys to produce golf equipmentwithout departing from the spirit or scope of this invention.

1. A precision casting process for golf club manufacture comprised of acasting process and a post-casting process, the casting processproducing metal alloy golf club components, the post-casting processconsisting of the steps of finishing the metal alloy golf clubcomponents and assembly of a golf club.
 2. A precision casting processas in claim 1, wherein the casting process is comprised of the steps ofdesigning a mold, selecting a metal alloy from the list of aluminum,magnesium, titanium, or steel, melting the metal alloy to a semi-solidstate, adding the semi-solid metal alloy to the mold, pressing thesemi-solid metal alloy into the mold with a ram to a pressure determinedby the selection of metal alloy, removing the metal alloy from the moldand cooling the metal alloy.
 3. A precision casting process as in claim1, wherein the casting process is comprised of the steps of atomizationof molten metal to form metal powders, sieving the metal powdersfollowed by gas classification to alter the particle size distribution,mixing the metal powders with thermoplastic binders to produce ahomogeneous feedstock, placing the feedstock into an injection molderand molding to form a net shape green part, removing the binder from thegreen part via evaporative debinding, sintering the part at hightemperature in a dry H₂ atmosphere or inert gas atmosphere.
 4. Aprecision casting process as in claim 2, wherein the metal alloyselected is titanium for face plate and sole plate components and thestep of finishing the metal alloy consists of annealing said face plateand sole plates, and where the metal alloy selected for the othercomponents is magnesium.
 5. A precision casting process as in claim 3,wherein the metal alloy selected is titanium for face plate and soleplate components and the step of finishing the metal alloy consists ofheating said face plate and sole plates, and where the metal alloyselected for the other components is magnesium.